Job1 07/09/2018 22:40:57 01/20/2019 11:48:52
Job2 11/28/2018 19:23:49 01/20/2019 05:29:49

Expected output:

Job1 2018/09/07 22:40:57 2019/20/01 11:48:52
Job2 2018/28/11 19:23:49 2019/20/01 05:29:49

Change text from dd/mm/yyyy to yyyy/mm/dd, i.e replace the text

  • Pay for your needs – 炸鱼薯条德里克 Jan 20 at 16:39
  • I did not understand, don't downvote simply..! – Vishwanath Dalawai Jan 20 at 16:42
  • @VishwanathDalawai I am not the downvoter, but I expect it's because you haven't provided any details of what you have tried so far. Please edit the question to include that information as well. – Haxiel Jan 20 at 17:19


$ echo -e "Job1 07/09/2018 22:40:57 01/20/2019 11:48:52\nJob2 11/28/2018 19:23:49 01/20/2019 05:29:49" | sed 's/\([0-9]\+\)\/\([0-9]\+\)\/\([0-9]\{4\}\)/\3\/\2\/\1/g' -
Job1 2018/09/07 22:40:57 2019/20/01 11:48:52
Job2 2018/28/11 19:23:49 2019/20/01 05:29:49

sed command explained:

's/pattern/replacement/' this is the basic syntax

When we put a g at the end (like 's/pattern/replacement/g') it will do multiple replacements on one line.

[0-9] matches any one digit.

[0-9]* matches zero or more digits.

[0-9]\+ matches one or more digits (note: the backslash \ is an escape character; in this example we needed to escape +, because otherwise the bash would interpret it, not sed; also note that in other circumstances/uses it does not have to be escaped).

\/ is a slash /; again it must be escaped, but now because of sed, because we used / as separator around and between pattern and replacement; we could use any other character (like 's@pattern@replacement@' and then we would not need to replace the slashes /, but the at @ character (or any other character we used as separator).

[0-9]\{4\} matches 4 digits; again { and } must be escaped because of bash.

([0-9]) matches any one digit and ‘saves’ it for later (to memory); then, in replacement we can use this matched substring that is enclosed in brackets ( and ) (in this case a single digit). Again, we needed to escape them because of bash.

\1 is the first saved substring (see the previous paragraph); likewise \2 is the second one and \3 is the third one.

Therefore: \([0-9]\+\)\/\([0-9]\+\)\/\([0-9]\{4\}\) matches a date in dd/mm/yyyy or d/m/yyyy format.

\3\/\2\/\1 is a replacement, which consists of \3 (the third substring, the year), \/ is a slash, \2 (the second substring, the month), again \/ (a slash), and finally \1 (the first substring, the day of month).

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